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Discussion Starter #1
So I recently did allot of research about the idle shudder and misfire at start up only to find that it is a common problem with almost all 08' GXP Solstice and Skys. Even after replacing the spark plugs with the newer "hotter" range for cold start characteristics, if your car warms up and drives normal except for when you stop and idle, you then get the dreaded "idle shudder" effect, then your fuel injectors could be at fault. I found several threads related to this same issue. Owners bringing in their cars time and time again with no results of finding the source of the problem until the fuel injectors are tested. Then they come back saying they need to be replaced because they are either leaking or just bad. So how many have had their injectors replaced on an 08' GXP or Redline? Seems to be only this year that has this problem. I think GM should fix this for free. My 08' only has 25k miles on it. The injectors should last longer than that.
 

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How much shudder does yours exhibit? Mine has a bit of an uneven idle (kinda like a 'lumpy' cam) but doesn't really shudder that much.
 

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Discussion Starter #3 (Edited)
How much shudder does yours exhibit? Mine has a bit of an uneven idle (kinda like a 'lumpy' cam) but doesn't really shudder that much.
When it idles at stop, it is very minor. Most people would not notice it if you did not tell them to wait for the vibration. I described it earlier in another post as a hickup. It's basically a misfire. It does not happen when the car is moving forward and under normal driving conditions, hence no code or check engine light will come on. If I have the stereo on with a song with allot of bass in it, and I "feel" it in my seat, that's the same feeling the misfire creates when sitting at idle. Morning starts are the same but it is the only time you can hear what sounds like a misfire from the exhaust. After the engine reaches operating temperature, the "morning misfire" goes away completely. Then you will only feel random shudders at idle through the day. The car will drive normal as if there is nothing else wrong. I like to describe it as my car has "the shakes" because I can feel it ever so slightly once in a while. It's random misfires, but only at idle. Like when you are sitting/waiting at a stop light. My 2.4 never had this problem. Always comes back to the 2.0 fouling plugs first that need to be replaced and then noticing that the fuel injectors are the cause for the premature changing of plugs.
 

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Then it seems the same as mine. Not sure why you're worried about it - I'm not.

The words and phrasing in the first post seem to make the symptoms appear far worse than they really are. :dunno:
 

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That may explain why mine tends to "load up" during idle. It only happens after I've been on the freeway and start to get into stop and go traffic. I have to rev it to 3k to clean it out and then it smoothes out for a minute or two....till it starts to shudder again. I always thought it was due to my goodies on it....
 

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Discussion Starter #6
I find the shuddering at idle very annoying. When I buy a car I expect it to run without any problems, or at least if it has a problem, make it so the it is fixable without having to "prove" it to the dealership that this is not normal. And a constant misfire IS something to worry about, it will only lead to more fouled plugs and early replacement of them. Not to mention individual cylinder damage in the long run.
 

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If you go on to other websites, it's recommended to replace the plugs on a turbo car every 15k (about every other oil change) because the pressure is so hard on the plugs.

Furthermore, I've worked almost my whole life in the dealership world....IT IS ALWAYS the customer's responsibility to prove an issue that is deemed normal operation by the manufacturer. The manufacturer has a specific set of guidelines they follow for what is normal and what isn't. If you think your fuel injectors have issues, I would advise you to take it to a reputable GM dealership and have them check it. If they say "no problem found, normal operation", then ask if their field service engineer can come out and check it out. Most would be happy to do so. But beware, if you have ANY non authorized GM aftermarket items on anything to do with the motor (even exhaust), nothing will be covered from a warranty standpoint. And if you're out of warranty and they find it's normal operation, they may tell you to put it back to normal specs if you have anything that is AM on it before they even bother to look at it. I had a buddy that had this issue with his RX8. He had an AM cat, and Mazda told him they wanted a Mazda cat on it before they would even think about engine replacement....so $1800 later, he got his engine warrantied.

And finally, it's a 4 cyl....and a high performance, turbo charged one at that!! It's going to have a "shudder"......Not to mention either, your car is 5 years old, you're going to have issues at that age....they don't last forever!
 

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Discussion Starter #8 (Edited)
It's going to have a "shudder"......Not to mention either, your car is 5 years old, you're going to have issues at that age....they don't last forever!
The shudder is not normal. I have driven a few of my friend's GXPs recently to see if theirs did this and none of them did it at all. One of them has an 07' and the other an 09' Coupe. Both GXPs and they have no shudder at idle.

Yes, my car is already 5 year old, but only has 25k miles on it and only had 20k on it when I bought it last year. For an 08' that's low millage. Certainly not the lowest, but definitely not high millage. I'm a firm believer that if you take care of your car with regular maintenance, they should last for a very long time. I realize all parts will eventually need replacement, but at 20-25k miles, that is way to soon.

As for my mods, the engine is completely stock. No mods, that's why I traded in my 2.4 for the 2.0, I wanted more power without having to add allot of mods. My mods so far have only been aesthetics, body kit, wheels, etc..

I have an appointment tomorrow at my dealership, I will keep everyone informed as to what they say.:chill:
 

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RedDevil,

Please keep us updated with the situation. Feel free to contact us if you any issues with the possible repairs. If you send a PM, include the VIN#, name, situation, contact information, dealership, and mileage. I hope this is taken car of quickly for you. Regards.

Matt,

GM Customer Assistance
 

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Discussion Starter #10 (Edited)
Dealership says it's fouled spark plugs. I bought the recommended spark plugs, AC Delco 41-108 because these have better cold starting characteristics. Went home, waiting for engine to cool down, installed new plugs. Still same results. Misfire at start up until car warms up, but no check engine light this time. Still has "shudder" at idle speed.

Can't afford to go back to the dealership right now. Girlfriend just got laid off last week so money is tight now with just one income. Will have to wait another 2 weeks until I get paid again so I can just leave my car with them and let them experiment with it. I still think it's the fuel injectors.
 

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I and a number of other folks I know have this very mine vibration at idle. There is not evidence it is harmful. Certainly the engine is not stressed at idle. Don't know way itis there but we have s complex, high performance piece of machinery with a lot of moving parts. I had to also learn to tune out the tick from the fuel pump, even after getting the insulator. Unless this is really much worse than we are understanding it to be, I suggest learning to ignore it.

Sent from AutoGuide.com App
 

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Discussion Starter #12
I and a number of other folks I know have this very mine vibration at idle. There is not evidence it is harmful. Certainly the engine is not stressed at idle. Don't know way itis there but we have s complex, high performance piece of machinery with a lot of moving parts. I had to also learn to tune out the tick from the fuel pump, even after getting the insulator. Unless this is really much worse than we are understanding it to be, I suggest learning to ignore it.

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I completely understand what you are saying, I know that the ticking sound from the high pressure fuel pump is normal and I can except that. But if the shudder is supposed to be "normal" then why don't ALL GXPs do this? Some do, and some don't. The shudder is caused by a misfire, and that is NOT normal. Plus, I'm still having the noticeable misfire at start up. And that is not only being felt, but being heard. Sounds like a back fire almost. That can't be good. Sure, once the car warms up it goes away, but I do not want to just ignore it, if it may turn into something worst in the future. Best to catch and fix the problem early before it turns into a bigger problem later.
 

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Red, is this cold idle problem something new or since you first got the car? The first 20,000 miles could be what is causing your idle to differ from the other GXPs you've cold idle tested. Abuse or mods that were removed. Try a thermal gun on the exhaust runners when at cold idle. See if any are heating up sooner or colder longer. Then check the other GXPs the same way to see if the temps differ. A low mount catch can on the breather tube might help the plugs last longer. Compression test cold and hot, wet and dry. Direct inj. is a great design but those little hammers are noisy as is the HPFP. Insulate. One last thing, give the turbo time to spool down before shutting off the engine, count to 10... Hope you get it figured out.
 

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We have two 08 Redlines:

My original engine tended to do the "shudder" fairly regularly at stoplight idle. But my first two years of ownership, I had much bigger issues to deal with. :lol: With the new engine, now about 23000 miles on it; I have a very minor "shudder" every now and then at idle.

My wife's redline has a very minor "shudder" at idle as well, every now and then. Her car has just shy of 30,000 miles.

I have a theory, that is probably hog wash; but here you go:
With the "normal" occasional "shudder" at long idle: We know the car will run certain self diagnostic tests on a regular basis. One of which is the EVAP test, to make sure the EVAP system is performing correctly. This test is done during extended idle periods. Another is the CAT test, which is also done some during extended idle, as well as other times. My theory is that the "normal shudder" we all pretty much experience is a result of one of the afore mentioned self diagnostic tests being run, and our DI reacting to the changed environment. It would be logical for the ECM to disable the misfire detection/code system during one of these self diagnostic tests; because of the likelihood of a misfire with the DI system during the test, because the DI tends to be very sensitive. IE: ECM runs EVAP test, and opens up the purge solenoid, thereby dumping a lot of fumes at one time into the intake. Thereby "flooding" the delicate A/F ratio at idle and probably resulting in a misfire. So the ECM disables the misfire detection during the EVAP test, because said misfire is considered "normal".

Now what you have going on, very well may be something else. For instance: one of the many issues I had early on involved a faulty wiring connection at the pigtail to the HPFP control solenoid. It was resulting in random/regular misfires and greater than normal "shuddering". The symptoms went on for some time, with no CEL; but there were stored misfire codes in history. It finally got bad enough to misfire pretty badly at WOT. Then it threw a CEL on the dash and misfire codes for every cylinder. :lol: The only way the tech was able to find the bad connection was by monitoring engine parameters via being plugged into the ECM with the Tech II (or something similar) and observing while going around and wiggling various wires. When he hit the bad pigtail to the HPFP control solenoid, it was very obvious. :lol: A classic example of having to be able to think outside of the "No Codes, No Problem" mentality.

I thought of something else today: When I had the purge solenoid for the EVAP system go bad, I had similar symptoms to what you are describing. Initially, I was experiencing a lot of stumbles/shuddering at idle during stoplights. Eventually I started having long crank issues, after filling the gas tank up. And finally it got bad enough to kill the engine when starting out from a stop, this happened a couple times. In my case the purge valve was sticking open and allowing fumes to flood the intake all the time. The system is supposed to only allow fumes to be purged during moderate throttle driving, where the extra fumes do not really interfere with the A/F ratio. Perhaps you have the beginnings of a bad EVAP purge solenoid?
 

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Discussion Starter #15 (Edited)
We have two 08 Redlines:

My original engine tended to do the "shudder" fairly regularly at stoplight idle. But my first two years of ownership, I had much bigger issues to deal with. :lol: With the new engine, now about 23000 miles on it; I have a very minor "shudder" every now and then at idle.

My wife's redline has a very minor "shudder" at idle as well, every now and then. Her car has just shy of 30,000 miles.

I have a theory, that is probably hog wash; but here you go:
With the "normal" occasional "shudder" at long idle: We know the car will run certain self diagnostic tests on a regular basis. One of which is the EVAP test, to make sure the EVAP system is performing correctly. This test is done during extended idle periods. Another is the CAT test, which is also done some during extended idle, as well as other times. My theory is that the "normal shudder" we all pretty much experience is a result of one of the afore mentioned self diagnostic tests being run, and our DI reacting to the changed environment. It would be logical for the ECM to disable the misfire detection/code system during one of these self diagnostic tests; because of the likelihood of a misfire with the DI system during the test, because the DI tends to be very sensitive. IE: ECM runs EVAP test, and opens up the purge solenoid, thereby dumping a lot of fumes at one time into the intake. Thereby "flooding" the delicate A/F ratio at idle and probably resulting in a misfire. So the ECM disables the misfire detection during the EVAP test, because said misfire is considered "normal".

Now what you have going on, very well may be something else. For instance: one of the many issues I had early on involved a faulty wiring connection at the pigtail to the HPFP control solenoid. It was resulting in random/regular misfires and greater than normal "shuddering". The symptoms went on for some time, with no CEL; but there were stored misfire codes in history. It finally got bad enough to misfire pretty badly at WOT. Then it threw a CEL on the dash and misfire codes for every cylinder. :lol: The only way the tech was able to find the bad connection was by monitoring engine parameters via being plugged into the ECM with the Tech II (or something similar) and observing while going around and wiggling various wires. When he hit the bad pigtail to the HPFP control solenoid, it was very obvious. :lol: A classic example of having to be able to think outside of the "No Codes, No Problem" mentality.

I thought of something else today: When I had the purge solenoid for the EVAP system go bad, I had similar symptoms to what you are describing. Initially, I was experiencing a lot of stumbles/shuddering at idle during stoplights. Eventually I started having long crank issues, after filling the gas tank up. And finally it got bad enough to kill the engine when starting out from a stop, this happened a couple times. In my case the purge valve was sticking open and allowing fumes to flood the intake all the time. The system is supposed to only allow fumes to be purged during moderate throttle driving, where the extra fumes do not really interfere with the A/F ratio. Perhaps you have the beginnings of a bad EVAP purge solenoid?
Here's an update. Just now went to lunch and the car drove totally normal! No misfires and no shudder at idle at all. Do spark plugs have a break-in period? Now I'm really confused. I guess I will just keep driving it and see what happens. I will keep everyone posted. Let's pray it is gone for good and problem solved.

Shadofax, yes, each cylinder has it's own coil pack. I even tried moving them around to see if the code for the check engine would follow. I did not. The misfire I had was still in cylinder #1. I park my car in an enclosed garage, but it can still get a little cold in there. Not as cold as the outside temp, but stays warmer. I did put some fuel injector/carb cleaner in my car a few weeks ago, but that is what I always do right after I have the oil changed.

I only got the check engine code to come on when the car was sitting for long periods in the garage with cold weather. But ever sense the first check engine light came on about 2 weeks ago, it has been misfiring at first start up in the mornings. Once the engine warms up, the car drives normal, except for the idle shudder I was having. This problem has been going on since last Nov. Let's just hope the new plugs are working properly now and every thing is back to normal. I did also check all of my electrical connections and did not see anything wrong.

Where is the evap purge solenoid located? I want to check all my electrical connections again.
 

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The ECM has to adjust to the new plugs. I did not want to respond to your other thread until you had driven the car for a few key cycles and some miles.
There still maybe other issues, but give the new plugs and the ECM a chance to get to know each other.
Drive it for a few days..........
 

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Shadofax, yes, each cylinder has it's own coil pack. I even tried moving them around to see if the code for the check engine would follow. I did not. The misfire I had was still in cylinder #1. I park my car in an enclosed garage, but it can still get a little cold in there. Not as cold as the outside temp, but stays warmer. I did put some fuel injector/carb cleaner in my car a few weeks ago, but that is what I always do right after I have the oil changed.

I only got the check engine code to come on when the car was sitting for long periods in the garage with cold weather. But ever sense the first check engine light came on about 2 weeks ago, it has been misfiring at first start up in the mornings. Once the engine warms up, the car drives normal, except for the idle shudder I was having. This problem has been going on since last Nov. Let's just hope the new plugs are working properly now and every thing is back to normal. I did also check all of my electrical connections and did not see anything wrong.
again.
First question.... The fuel injector/carb cleaner....is it the $20/bottle stuff or is it the $2.39 stuff? If its the later, it does VERY LITTLE (and may do more harm then good in these engines) and you're really just wasting your money. If you want to have your fuel injectors cleaned, have the dealership do it every 20 to 30k. Maybe someone else can chime in on this, but that's always been my understanding, and I have worked in the dealership world....

Next item, as was stated earlier, you need to have, AT THE VERY LEAST the #1 cylinder pressure tested. Not implying anything, but you may have a valve not seating properly, you could have a blown head gasket, a cracked head, something that has to do with heat....

GSStage1, I have this idle shudder he's speaking of, but I don't have any stored codes at all. The only code EVER in my car was from an O2 sensor. And my guess is that was when the high flow cat was put on before I owned it.

Bottom line RedDevil, the car needs to be checked, and if you're not happy with the results, tell them to have a field service engineer come out and check it out. If you have a CEL, they should be able to accommodate you with the FSE after they've told you its just the plugs again. If you've had the plugs changed there, that's your ammo to get the FSE out there....especially if its been within so many months/miles.....
 

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Discussion Starter #20
Here's an update. My car has "morning sickness" :lol: It only sounds like a misfire, or hell I don't know maybe it's a backfire I'm hearing instead, not really sure, but it only last for a few seconds. Once the RMP lower to 8-9K RPM the rumble I hear goes away completely. The car drives fine for the rest of the day. The best news so far is that the "idle shudder" has gone away completely and has not returned. The car drives normal as long as the engine temperature has reached it's warming level. Once I leave it sitting for a few hours and the engine gets cold again, the rumbling at start up comes back until it warms up again. I guess as long as the car drives well I should not be to worried. i just wish it would go back to starting like it used to. I think I just need to put more miles in it with the new plugs in it. So far I've put 35 miles on it in the past 2 days. I'm just glad the shudder is gone when idling.
 
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